This invention relates generally to the area of treatments for circulatory shock and more specifically to a solution which is both hyperosmotic and hyperoncotic for use in preventing and treating hypodynamic shock.
Trauma is the major cause of death in persons under 38 years of age and accounts for over 150,000 deaths per year in this country. Among the most hazardous consequences of traumatic injury is bleeding. The loss of more than 50% of the starting blood volume is not unusual in such injuries and is fatal if not treated promptly.
While field therapy of many medical emergencies, such as cardiac arrest, asthmatic attacks and diabetic crisis has become increasingly successful due to the ever increasing armanentarium of effective drugs, considerably less success has been realized with field treatment of trauma and shock. No drugs have proven effective for the initial treatment of trauma victims. Initial therapy of trauma and hemorrhage currently centers on effecting the cessation of bleeding and on the infusion of large volumes of solutions to replace lost blood volume. Large volume infusion (2 to 8 liters) has generally been considered necessary to restore normal circulatory functions such as arterial blood pressure, cardiac output, oxygen consumption and renal function. Such treatment must be accomplished rapidly to be effective.
The infusion of large volumes of solution involves risks and complications, however. Fluid overload, or "overexpansion", and congestive pulmonary atelectasis may result after use of excessive amounts of fluid. Limited personnel and difficult conditions at the site of an accident make adequate field resuscitation difficult to impossible. In addition to the time necessary merely to infuse such volumes, critical minutes are lost due to difficulties in gaining access to the vascular system. Paramedical personnel must be highly trained to perform such operations. As a result, the average trauma patient has received only 700 ml of fluid prior to arrival in the emergency room, a volume which is normally insufficient to effectively treat hypodynamic shock.
Fluid replacement infusion normally utilizes solutions which have a similar osmolarity to blood plasma. Osmolarity refers to the total concentration of molecules or solutes in a solution. Water will tend to move across a semi-permeable membrane into a solution having a higher concentration of solutes. Thus, the introduction into, for example, the blood vessels, of a fluid having an osmolarity higher than that of normal body fluids will establish an osmotic gradient across the membranes, resulting in an initial change of fluid volume within the vascular system. Osmolarity is generally expresses as millimoles per liter of solution or mOsms.
Small molecules will themselves gradually leak out of the blood vessels, however, so that vascular volume will return eventually to preinfusion levels. Larger molecules, such as colloids, will not escape from the blood vessels as easily, and thus will maintain an osmotic gradient across the membranes. Because the osmotic pressure exerted by colloids in the blood, which is in the range of about 1 to 2 mOsms, is so much smaller than that of the total osmotic pressure generated by all solutes, colloidal osmotic pressure, or oncotic pressure, is expressed in terms of mm Hg. Blood plasma has an osmolarity of about 283 to 295 mOsms and an oncotic pressure of about 25 mm Hg. Solutions which exceed these levels are termed hyperosmotic or hyperoncotic, respectively.
Recently, attempts have been made to treat animals in hypodynamic shock with highly hyperosmotic saline solutions, having an osmolarity in the range of 2400 mOsms. Such treatment has the advantage of requiring smaller total fluid volume and results in brief initial promotion of circulatory function. Because this improvement is short-lived, however, with critical parameters deteriorating over time, hyperosmotic saline does not provide an effective, sustained treatment for shock.
There thus exists a longfelt need for an effective solution for treating shock victims, particularly those experiencing hypodynamic shock. Administration of a small volume of such a solution should result in the rapid and susstained normalization of circulatory function. Additionally, the solution should be inexpensive and have a long shelf life. The present invention satisfies these needs and provides related advantages as well.